The gunman who held hostages for more than 16 hours in a Sydney cafe was no stranger to police -- and was on bail for violent criminal offenses at the time of the siege .

Man Haron Monis , an Iranian-born refugee who was granted political asylum in Australia in 2001 , had `` a long history of violent crime , infatuation with extremism and mental instability , '' Australian Prime Minister Tony Abbott told reporters .

`` It 's pretty obvious that the perpetrator was a deeply disturbed individual , '' he said at a press conference Tuesday , adding that the 50-year-old was `` well known '' to federal and state police , as well as the Australian Security Intelligence Organization .

`` But I do n't believe he was on a terror watch list at this time . ''

New South Wales Premier Mike Baird said authorities were investigating why Monis -- who was killed in the siege -- was at large , given his criminal background .

`` We 're all outraged that this guy was on the street , '' he told reporters . `` We need to understand why he was . We also need to understand why he was n't picked up . ''

What we know , what we do n't know

Accessory to murder , sex charges

The self-styled Muslim cleric , also known as Sheikh Haron , was facing dozens of charges at the time of the siege , including two counts of being an accessory to the murder of his ex-wife , according to the Attorney General of New South Wales .

Noleen Hayson Pal was found dead with multiple stab wounds in a stairwell , and her body had been set on fire , The Sydney Morning Herald reported .

`` They should have put him away and thrown away the key , '' the dead woman 's godfather , Ayyut Khalik , told NBC News . He said Monis used to beat Pal , forcing her to wear a hijab all the time and forbidding her from talking to `` outsiders . ''

Court documents show Monis was also facing 45 sex-related charges , including sexual intercourse without consent and aggravated indecent assault .

According to the Sydney Morning Herald , the initial charges , laid in May 2014 , related to an alleged sexual assault on a woman in western Sydney in 2002 , before other sex-related charges were added regarding six additional victims .

Monis was using the name Mohammad Hassan Manteghi -- his birth name , according to Iran 's state news agency IRNA -- and claimed to be a `` healer , '' according to the report .

Monis also pleaded guilty last year to writing offensive `` poison pen '' letters to the families of Australian soldiers who died in Afghanistan , and was sentenced to 300 hours of community service . The letters were `` sadistic , wantonly cruel and deeply wounding , '' one High Court judge said at the time , according to CNN affiliate Seven News .

But the criminal accusations against him began even before he came to Australia .

Monis fled his homeland in 1995 while being sought for allegedly committing fraud , Iran 's semi-official Fars News reported .

A spokesperson at Iran 's embassy in Canberra told CNN that Tehran had officially requested Monis 's extradition but nothing had come of it . Monis had been granted political asylum in 2001 and had had no further contact with his birth country , the spokesperson said .

Who were the victims ?

An extremist theology

Manny Conditsis , a lawyer who acted for Monis in relation to the accessory to murder and letter-writing charges , told CNN his former client had been a cleric in Shiite Iran , but had become critical of the Islamic Republic 's government in the late 1990s , and fled to Australia `` because he was going to be killed . ''

He had left behind a wife and two children , who he believed Monis had not seen since .

Throughout the 2000s , said Conditsis , Monis `` became sympathetic to what he perceived ... was the victimization of Muslims and Islamists around the world , and partly at least took up that cause . ''

His broader cause , he said , was lobbying governments around the world , particularly Australia , not to wage wars on Muslim soil .

`` He was so blinded by that objective that it would seem he had lost sight of objectivity and rationality and acted in extreme ways , '' he said , describing his former client as `` intensely conflicted and contradicted and inconsistent . ''

While older footage of Monis preaching shows him dressed in typical Shiite cleric 's attire , in his social media posts , he appears to embrace a radical Sunni extremist theology .

He used the Internet to spread extremist beliefs , garnering nearly 13,000 likes on his Facebook page .

During the siege , Abbott said , the hostage-taker `` sought to cloak his actions with the symbolism of the -LRB- ISIS -RRB- death cult , '' Abbott said .

On his website , which has now been taken down , there was a pledge of allegiance to the so-called Islamic State terror group .

The site describes Monis as a Muslim cleric and activist based in Sydney who has `` continuously been under attack & false accusation by the Australian government & media since he started his political letter campaign from 2007 . ''

There 's a graphic photo of slain children at the top of the site . Under the image , it reads , `` This is an evidence for the terrorism of America and its allies including Australia . The result of their airstrikes . ''

A description on the site portrayed Monis as a victim of a political vendetta and compares him to Julian Assange , the WikiLeaks founder who has claimed the sex crime allegations he faces are politically motivated .

A YouTube video posted in November shows Monis standing on a street corner , chains draped over him , carrying a sign that says , `` I have been tortured in prison for my political letters . ''

Police have refused to comment on that accusation .

His last tweet linked to his website , with a haunting message posted the day of his attack on the Sydney cafe : `` If we stay silent towards the criminals we can not have a peaceful society . The more you fight with crime , the more peaceful you are . ''

Conditsis told Australian public broadcaster ABC that Monis was an isolated figure who was probably acting alone .

Crisis in a cafe

Monday 's hostage situation began around 10 a.m. Hundreds of police officers , including snipers , took position around the Lindt Chocolate Cafe in Sydney 's central business district .

Australian media captured haunting images of hostages pressing their hands against the cafe 's windows . They were reportedly taking turns holding a black flag with Arabic writing on it that said , `` There is no God but God and Mohammed is the prophet of God . ''

The man holding the hostages demanded to speak to Abbott . Police were monitoring social media because hostages appeared to be posting information about the man 's demands .

Hours into the crisis , at least five hostages managed to escape , running terrified toward police in riot gear . That made the hostage-taker furious , reported Chris Reason , a correspondent for CNN affiliate Seven Network . Reason said he could see the gunman become `` extremely agitated '' when he realized what had happened , and he `` started screaming orders '' at the remaining hostages .

Gunfire erupted early Tuesday as police stormed the cafe where the gunman had been holding hostages .

Two hostages were killed during the standoff . Police later announced that the siege was over and that the lone gunman had been killed .

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Man Haron Monis had history of `` infatuation with extremism and mental instability , '' Abbott says

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Hostage-taker was granted political asylum in Australia in 2001 ; was on bail for violent offending

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His former lawyer says he campaigned against `` the victimization of Muslims and Islamists ''

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On Monis ' apparent website , there is a pledge of allegiance to ISIS